If you'd like you can easily alter commonly used emoticons (-; -P for example) with custom smilie pictures. This can be done from the category named Smilies. From the Smilie Manager you can list, edit and delete the currently available smilies, add and manage categories.
New smilies can be uploaded from the Upload Smilie functionality. Browse for the image file from your local computer, set the new smilie title and the emoticon that matches. Default values are picked for the category, the relative path and the display order.
Click on the Upload button and you are done. A new smilie is added.